Many commercial soluble coffee products are enhanced with volatile aromatic compounds by combining the soluble coffee product with pure coffee oil or aroma-enriched coffee oil so as to provide the soluble coffee product with an aromatic quality more like that of roasted and ground coffee. However, aromatizing a soluble coffee product with coffee oil presents plant processing problems in recovery of the oil from the roasted coffee beans and processing of the retaining deoiled coffee beans and in storage of the oil.
Generally, headspace aromatization of soluble coffee products without the use of coffee oil as an aroma source or aroma carrier has not met with marked commercial success. It is known that conventionally produced soluble coffee solids lack the capacity or property of sorbing, retaining and releasing volatile aromatic compounds such as are contained in, or added to, coffee oil.
In applications Ser. Nos. 950,337 and 086,367, now applications Ser. Nos. 189,515 and 235,506 hereinbefore referred to, porous soluble coffee particles having the capacity to sorb large quantities of volatile aromatics, to retain the aromatics for extended periods of time, and subsequently, to release the aromatics under repeated in-use conditions such as may be encountered in opening and closing a container in which the particles are packaged are described and claimed. The aromatized soluble coffee particles may be added in small amounts and mixed with or added to unaromatized soluble coffee solids to provide a soluble coffee product with a desirable coffee aroma such as the aroma of freshly roasted and ground coffee.
The porous soluble coffee particles having an average diameter of less than 200 microns are characterized as being microporous, that is, by having a microporous structure wherein the most probable radius of the pores is 150 A or less and the pore volume per gram of dry soluble coffee solids is from 3 to 30 microliters per gram. These microporous structured soluble coffee particles are prepared by instantaneously freezing an aqueous extract or solution of coffee solids as by spraying the extract solution into a cryogenic fluid and subsequently freeze-drying the frozen particles, spheres or granules.
While the methods described and claimed in the hereinbefore mentioned patent applications are capable of producing microporous structured soluble coffee, there would be advantages to preventing entrainment losses in the freeze-drying equipment which losses may result when the size of the individually frozen particles, granules or spheres as prepared by freezing a spray is not optimized. Further, there would be advantages to an even more controlled freezing method or process so that the freezing rates and, thus, the ice crystal size might be more carefully controlled.